Dynamic range limits in field determination of fluorescence using fiber optic sensors

Wayne Chudyk; Kenneth Pohlig

doi:10.1117/12.24780

1 March 1991 Dynamic range limits in field determination of fluorescence using fiber optic sensors

Wayne Chudyk, Kenneth Pohlig

Proceedings Volume 1368, Chemical, Biochemical, and Environmental Fiber Sensors II; (1991) https://doi.org/10.1117/12.24780
Event: SPIE Microelectronic Interconnect and Integrated Processing Symposium, 1990, San Jose, United States

Abstract

Prior work has reported on the usefulness of fiber optic sensors in detection of aromatic organic ground water contaminants such as the benzene toluene ethylbenzene and xylenes (BTEX) fraction of petroleum fuels. Our device is essentially a laser fluorimeter using fiber optic sensors for in-situ measurements. Both field and laboratory work have exhibited limits in the dynamic response range of fluorescence signal versus concentration when excitation occurs in the ultraviolet (266 nm). Potential causes of the observed shallow fluorescence versus concentration response include self-absorption at high concentration and stray light or electronic noise at low concentrations. The observed wide dynamic range resulting from visible excitation (532 nm) is used as a basis for comparison with UV performance. Selfabsorption phenomena are evident from the data at high contaminant concentration but practical applications more often are concerned with low concentrations. Lower limits of detection observed in UV excitation experiments are evaluated as to the possible sources of stray light including fiber luminescence coupling between the excitation and collection fibers in the sensor elastic scattering and reflection signals in the excitation module and spectral impurities in the laser excitation light from the laser flashlamp. Coupling and fiber luminescence in the sensor have been evaluated and resolved the excitation module has been redesigned to reduce potential scattering and the laser source continues to be investigated. 1 . LASER-INDUCED FLUORESCENCE TECHNIQUE Our research group has been

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Wayne Chudyk and Kenneth Pohlig "Dynamic range limits in field determination of fluorescence using fiber optic sensors", Proc. SPIE 1368, Chemical, Biochemical, and Environmental Fiber Sensors II, (1 March 1991); https://doi.org/10.1117/12.24780

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